Had a severe issue with Samba server recently: it refused to serve after some undefined amount of time. It could work for a days perfectly or could be completely unreachable in several minutes after restart. Logs were useless, even in the highest possible debug level.

The problem was found accidentally. I have some information in national language and I usually edit /etc/samba/smb.conf from X environment or msWindows, using Unicode-aware editors. But at some time share comments in config file were edited using pico in ISO-8859-1 terminal. Pico is perfect editor for me (i hate complexity of vi or emacs) , but in this case the combination of wront terminal and ANSI-type editor was lethal. The UTF-8 strings were mangled and the configuraton was wrong (althow `testparm` showed it’s OK).
So, don’t do this at work 😉